1. Field of the Invention
The subject matter of this invention is related to circuit interrupters generally and more particularly to gas evolving slot motor arrangements for driving the electrical arc away from opening contacts.
2. Description of the Prior Art
Slot motors are well known in the art. Reference can be made to U.S. Pat. No. 3,815,059 to Spoelman issued Jun. 4, 1974 entitled "Circuit Electro-Magnetic Opening Means" and assigned to the assignee of the present application. A slot motor is a device made of magnetic material which surrounds the contact arms of a circuit breaker such as a molded case circuit breaker. As the electrical contacts which are interconnected with these arms begin to separate because of the movement of the arms away from each other an electrical arc is drawn between the separating contacts which contains the electrical currents still being carried by the separating contacts and which flows through the arms. The electrical current interacts electromagnetically with the slot motor to induce a magnetic field in the magnetic material of the slot motor which in turns interacts with the separating contact arms to accelerate the contact opening process. Another example is found in U.S. Pat. No. 4,970,482 issued Nov. 13, 1990 to Jacobs et al, entitled "Current Limiting Circuit Breaker Arc Chute Configuration".
It has also been known in the past to utilize sheets of gas evolving material in the vicinity of the opening contacts to interact with the heat of the arc to evolve pressurized gas which has a tendency to push the arc away from the separating contacts into an arc chamber where it is cooled and interrupted thus assisting in interrupting the flow of the current. Such an example may be found in U.S. Pat. No. 4,485,283 issued Nov. 27, 1984 to Hurtle and entitled "Current Limiter Unit".
It is also known to support one of the contacts so that it remains fixed relative to the other rapidly moving contact and contact arm. The fixed contact is usually interconnected with one of the terminals of the circuit breaker by way of a loop so that the current flowing both in the fixed contact arm and the movable contact arm are flowing in the same direction. The advantage of this is that the magnetic forces acting on the contact arm as a result of the same direction current flow tend to assist in separating the contacts more rapidly.
It would be advantageous therefore if a single device could be found which acts both as a slot motor, a gas evolving material and a contact support.